U.S. Pat. No. 5,333,579 issued Aug. 2, 1994 and U.S. Pat. No. 5,557,983 issued Sept. 24, 1996 disclose a VVA apparatus of the above kind. This known apparatus comprises a driving shaft having a shaft axis of rotation, a driving member fixed to the driving shaft for rotation about the shaft axis, a driven member movable relative to the driving shaft for rotation about the shaft axis. The driven member has an integral cam controlling an engine cylinder valve. An intermediate member is drivingly connected between the driving and driven members. A support has mounted therein the intermediate member mounted for rotation so as to rotate concentrically or eccentrically with respect to the shaft axis. The support is held for movement within a plane perpendicular to the shaft axis. A control rod has an integral eccentric cam received in a radial slot cut inwardly into the support. The support is also formed with a second opening that receives a pivot shaft fixed relative to the engine cylinder head. Rotating the control rod from one angular position to another angular position causes the eccentric cam to move the support about the pivot shaft, causing the intermediate member to rotate eccentrically with respect to the shaft axis. Reverse rotation of the control rod from the another angular position to the one angular position cause the intermediate member to rotate concentrically with respect to the shaft axis.
Similar VVA apparatuses are disclosed in U.S. Pat. No. 5,365,896 issued Nov. 22, 1994, U.S. Pat. No. 5,501,186 issued Mar. 26, 1996, and U.S. Pat. No. 5,687,681 issued Nov. 18, 1997.
JP-A 7-119425 teaches the use of control rod holding brackets in holding supports for movement within a plane perpendicular to the shaft axis of the driving shaft and a control rod. The control rod holding brackets are mounted to the cylinder head in addition to spaced cam brackets. The cam brackets are spaced one after another along the shaft axis and supports driven hollow camshafts. A sub-assembly is proposed which includes the control rod holding brackets, bearing caps, and the supports, and the control rod. The control rod holding brackets and the mating bearing caps are recessed inwardly away from each other to receive the control rod for rotation about a control rod axis. Each of the control rod holding brackets carries a pin for rotation about a pin axis. Each of the pins is received in a slot cut inwardly of one of the supports for allowing relative rotational and radial movement of the support to the bracket with respect to a centerline of the pin. The control rod has axially spaced eccentric cams, which are received in openings of the supports, respectively. After completion of assembly on an engine cylinder head, the control rod is drivingly connected to the supports. In operation, the control rod and the pins bear stress imparted to the supports due to valve springs of the engine cylinder valves. During eccentric operation mode, each of the intermediate members is subject to acceleration and deceleration under rotation of the driving shaft at a constant speed. To minimize cylinder-to-cylinder variability in valve lift characteristics, it is demanded to keep the amount of eccentricity of an axis of rotation of each of the intermediate members with respoect to the shaft axis of the driving shaft unaltered. However, the control rod is susceptible to flexure owing to the valve springs during the eccentric mode operation, causing the cylinder-to-cylinder variability in the eccentricity. Thus, the control rod holding brackets have to support the control rod at locations in the vicinity of portions where the control rod bears the stress of each of the supports. The known control rod holding brackets require mounting areas on the cylinder head in the vicinity of the adjacent supports.
An object of the present invention is to suppress the flexure of the control rod of the VVA apparatus of the above kind with a control rod holding structure that does not require mounting areas on the cylinder head in the vicinity of the adjacent supports.